Container packaging method

ABSTRACT

A container packaging method is provided which ensures a sealing ability and yet has an easy opening ability. Between a container edge ( 1 ) and a film covering an upper opening face of a container, a strip seal ( 3 ), having a portion sealed partially weakly at an outer side portion of a corner of the container edge ( 1 ), is formed and a double line seal  5, 6  is formed on the strip seal ( 3 ). An outer line seal ( 5 ) has its corner end projected toward an outer side edge of the corner of the container edge ( 1 ). The outer line seal ( 5 ) and an inner line seal ( 6 ) are connected by a seal connection ( 8 ) formed in a diagonal direction B-B of the container. The inner line seal ( 6 ) has its inner side edge at the corner of the container edge ( 1 ) formed in a cornered shape ( 9 ).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a container packaging method for packaging a container, having a container edge and being filled with an article, by covering an upper opening face of the container by a film and effecting a seal of an overlapped portion of the container edge and the film.

[0003] 2. Description of the Prior Art

[0004] Nowadays, there are provided in the markets an extremely large number of articles that are packaged in containers. Among them, like tofu, or bean curd, packaged in the containers, there are seen many articles that are packaged by covering an upper opening face of the container, filled with the articles, by a film and effecting a seal of an overlapped portion of a flange-like container edge and the film.

[0005] In such packaged articles that are packaged by covering the upper opening face of the container and effecting the seal of the overlapped portion of the container edge and the film, the articles can be tightly sealed in the container so as to be kept clean, liquid or juice also can be sealed and shapes of the articles can be kept by the strength or rigidity of the container. Thus, such a packaging is widely employed for many kinds of articles.

[0006] With respect to the packaged articles of the abovementioned kinds, in order for the packaged liquid or juice not to leak outside, the sealing ability between the container edge upper surface and the film must be ensured. But, on the other hand, when the articles are to be taken out of the container, it is desirable that the film on the container can be easily and smoothly peeled off without an excessive force being added. Especially, like the packaged tofu, when the articles are sealed in the container together with liquid or juice, it is particularly desired that the container can be opened only with a smooth opening action so that the liquid or juice may not spill outside when the film is being removed.

[0007] In order to ensure the strength, the sealing ability, etc. at the same time, the container and the film, respectively, used for the article packaging are usually formed in a laminate in which a plurality of sheets or films are laminated. For example, the container is formed in a multilayer structure in which a core portion made of polystyrene is sandwiched between upper and lower surfaces made of polypropylene and the film is a laminate sheet made of nylon and polypropylene, so that the container and the film are joined together by a seal via the polypropylene surfaces.

[0008] As the container and the film are so formed by the multilayer sheet or multilayer film, if they are joined together too strongly, the sealed portion is hardly peeled at the time of opening the container, so that an interlayer peeling may occur in the laminated film or container. Thus, the container cannot be smoothly opened and there is often caused a problem, such as jumping out or spilling of the articles or liquid in the container. Or, otherwise caused is a problem, such as tearing of the film in the middle of the sealed portion between the container and the film because of difficulty in opening the container along the sealed portion or breaking of the film on the container to cause a half-opening of the container. Hence, there has been often caused such a case that the container had to be opened by cutlery.

[0009] Also, in order to open the container, as the film on the container edge has only a small pulling tab at a corner portion of the container, it is not always easy to lift the small tab to peel the sealed portion and, moreover, a considerable force is required to pull the tab. Hence, at the very moment when the sealed portion begins to peel or when the film is suddenly broken, the container is necessarily moved, which often resulted in scattering the liquid or juice out of the container or upsetting the container.

[0010] It is therefore an object of the present invention to provide a container packaging method for packaging a container, having a container edge and being filled with an article, by covering an upper opening face of the container by a film and effecting a seal of an overlapped portion of the container edge and the film, by which a sealing ability at the sealed portion is ensured and still the film on the container edge upper surface can be smoothly and easily removed along the sealed portion without an excessive force being added, so that a container package having an easy opening ability is obtained.

SUMMARY OF THE INVENTION

[0011] In order to achieve the abovementioned object, the present invention provides a container packaging method for packaging a container, having a container edge and being filled with an article, by covering an upper opening face of the container by a film and effecting a seal of an overlapped portion of the container edge and the film, comprising the step of effecting the seal at a corner of the container edge in a shape that the seal has its corner end projected toward an outer side edge of the corner of the container edge.

[0012] According to the container packaging method of the above invention, at the corner of the container edge, the seal between the container edge upper surface and the film covering the container edge upper surface has its corner end projected toward the outer side edge of the corner of the container edge. Thus, when the film is being lifted to be peeled from the corner of the container edge, the peeling force given on the film concentrates on the projected end of the seal and the seal is easily peeled from the projected end. Hence, starting from the projected end, the film that is attached to the container edge upper surface by fusion can be smoothly peeled along the seal.

[0013] In the container packaging method according to the present invention, at the corner of the container edge, it is preferable that a non-sealed portion is provided between the outer side edge of the corner of the container edge and the projected end of the seal that is projected toward the outer side edge of the corner of the container edge. By so doing, when the film is to be peeled at the corner portion, the peeling force is easily concentrated on the projected end of the seal and the film can begin to be easily and smoothly peeled.

[0014] Also, by providing the above non-sealed portion at the corner outer side of the container, that is formed in a laminate, when the film, that is attached to the container edge upper surface by fusion, is to be peeled, there is caused no opportunity of an interlayer peeling that begins from the container end portion. Hence, only the fusion portion of the film can be peeled without causing the interlayer peeling in the container.

[0015] Also, in the container packaging method according to the present invention, at the corner of the container edge, it is preferable that the seal has its inner side edge formed not in a rounded shape but in a cornered shape. By so doing, when the film further proceeds to be peeled from the container edge, the peeling force is concentrated on an apex of the cornered shape and the container edge upper surface, to which the film is attached by fusion to form the seal, is separated or cut off from the fusion portion at the place of the apex of the cornered shape. Thus, without causing the interlayer peeling in the container, the film can be continuously peeled.

[0016] Also, in the container packaging method according to the present invention, the seal between the container edge and the film may be formed in a line seal so that the seal is tightly effected. In this case also, the film can be easily peeled along the seal starting from the projected end of the seal projected toward the corner end of the container edge.

[0017] In this case, in order to ensure the sealing ability, the line seal may be formed in a multiple line seal having a plurality of line seals. If the plurality of line seals at the corner of the container edge are connected to one another in a substantially diagonal direction of the container, the peeling force is smoothly transmitted to the inner side seal along the seal in the diagonal direction. Thus, a container package in which the film can be easily and smoothly peeled can be obtained.

[0018] Furthermore, in order to achieve the above-mentioned object, the present invention provides a container packaging method by which a seal structure ensuring a sufficient sealing ability is constructed between the container edge and the film covering the upper opening face of the container such that, in addition to any of the line seals as mentioned above, a strip seal is formed having a portion that is sealed partially weakly at an outer side portion of a corner of the container edge, so that an overlapped seal of the strip seal and the line seals is obtained.

[0019] As the strip seal of the seals formed by the container packaging method of the present invention has the portion that is partially weakly sealed at the outer side portion of the corner of the container edge, the film can be easily and smoothly peeled from the corner portion of the container. When the peeling reaches the line seal, the line seal can be easily and smoothly peeled from the projected end of the seal that is projected toward the outer side edge of the corner of the container edge, as mentioned above.

[0020] Also, in the case where the line seal is formed in the multiple line seal, the peeling force is smoothly transmitted to the inner side seal along the seal in the diagonal direction that is formed at the corner of the container edge and the seal can be easily peeled.

[0021] As described above, according to the container packaging method of the present invention, a container package ensuring a sealing ability and yet having an easy opening ability can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a plan view showing a strip seal formed by a first step in an embodiment according to the method of the present invention.

[0023]FIG. 2 is a plan view showing a line seal formed by a second step in the embodiment of FIG. 1.

[0024]FIG. 3 is an enlarged plan view of corner portion A of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Herebelow, the container packaging method according to the present invention will be described more concretely based on an embodiment shown in the figures.

[0026] The container packaging method of the present invention to be described below is an example based on the embodiment comprising two steps to form a seal between a container edge and a film that covers an upper opening face of a container.

[0027] (First Step)

[0028] In the first step, a strip seal is formed between a container edge upper surface of the container and the film. In FIG. 1, that is a plan view showing the strip seal formed by this first step, numeral 1 designates a container edge and numeral 2 designates an article, like tofu, filled in the container. The upper opening face of the container is covered by the film and a strip seal 3 is formed between the film and the container edge upper surface. At a container edge outer side portion of each of four corners of the strip seal 3, there is formed a weakly sealed portion 4 that is sealed partially weakly.

[0029] In order to form the strip seal 3, the film, while being lapped over the container edge 1, is pinched between a sealer and a platen to be sealed by a conventional art as usually carried out. Also, the weakly sealed portion 4 may be formed by using a sealer or platen made in such a shape as having partially concave portions. Thus, the strip seal 3 is formed having the weakly sealed portions 4 at the four corners from which the film begins to be peeled when the container package is to be opened.

[0030] In the course of forming the strip seal 3, fractions or scraps of the article 2, that have attached to the container edge 1 at the time of filling the article 2 in the container, are removed by the sealing pressure. Needless to mention, the sealing conditions of the sealing pressure or temperature, etc. are to be set to appropriate values in consideration of materials of the container and the film, kinds of the article 2 to be filled, sizes of the container, strength of the sealing ability, etc.

[0031] (Second Step)

[0032] Subsequently, in the second step, a double line seal is formed on the strip seal 3 that has been formed by the abovementioned first step. The second step will be described below with reference to FIGS. 2 and 3.

[0033] In FIGS. 2 and 3, numerals 5 and 6 designate the double line seal formed between the container edge 1 and the film, wherein 5 is an outer line seal and 6 is an inner line seal. The double line seal 5, 6 is provided as a seal that is stronger than the strip seal 3 and is formed so as to be lapped over the strip seal 3 that has been formed in the first step. Incidentally, illustration of the strip seal 3 is omitted in FIGS. 2 and 3 for easiness of understanding.

[0034] At each of the corners of the container edge 1, the outer line seal 5 has a seal projection 7 that projects toward an outer side edge of the corner of the container edge 1. There is provided a non-sealed portion C between a projecting end of the seal projection 7 and the outer side edge of the corner of the container edge 1. Also, at each of the corners of the container edge 1, there is provided a seal connection 8 that connects the outer line seal 5 and the inner line seal 6 in a substantially diagonal direction B-B of the container. An inner side edge of the inner line seal 6 at each of the corners of the container edge 1 is formed not in a rounded shape but in a cornered shape 9.

[0035] Needless to mention, the sealing conditions of the sealing pressure or temperature, etc. for forming the line seals 5, 6 are to be set to appropriate values in consideration of materials of the container and the film, kinds of the article 2 to be filled, sizes of the container, strength of the sealing ability, etc.

[0036] According to the container packaging method of the present invention as described above with respect to the embodiment, there are formed the strip seal 3 and the double line seal 5, 6 between the container edge 1 and the film thereon, and the strip seal 3 has the weakly sealed portion 4, that is sealed partially weakly, at the outer side portion of each of the corners of the container edge 1. Thus, when the film covering the container upper face is grasped to be lifted at the corner end of the container, the film can be easily peeled from the weakly sealed portion 4.

[0037] Moreover, the outer line seal 5 has the seal projection 7 projecting toward the outer side edge of each of the corners of the container edge 1. Hence, when the film covering the container upper face is lifted at the corner end, as mentioned above, the film is first lifted at the non-sealed portion C that is provided between the projecting end of the seal projection 7 and the outer side edge of the corner of the container edge 1. Thereby, the lifting force acting on the film concentrates on the projecting end of the seal projection 7, so that the projecting end of the seal projection 7 is smoothly peeled and, starting from the peeling of the seal projection 7, the outer line seal 5 is also smoothly peeled along the line of the outer line seal 5.

[0038] The peeling force of the outer line seal 5 is transmitted to an outer side of a corner of the inner line seal 6 via the seal connection 8 and the inner line seal 6 is thereby smoothly peeled starting from the seal connection 8. The inner side edge of the inner line seal 6 is formed in the cornered shape 9 and thus a fusion portion forming the seal between the upper surface of the container edge 1 and the film is cut off at an apex of the cornered shape 9 and there is caused no interlayer peeling in the sealed portion of the container material that is formed in the laminate.

[0039] Subsequently, the film is further peeled smoothly along the strip seal 3 and the line seals 5, 6.

[0040] Thus, according to the container packaging method of the present invention as described with respect to the embodiment, the sealing ability between the container edge land the film covering the container is sufficiently ensured by the strip seal 3 and the strong double line seal 5, 6.

[0041] In the seals formed as described above, the strip seal 3 is easily and smoothly peeled starting from the weakly sealed portion 4, the outer line seal 5 starting from the projecting end of the seal projection 7 and the inner line seal 6 starting from the seal connection 8.

[0042] Also, the peeling force acting on the film is prevented from being transmitted to the sealed portion of the multilayer material of the container.

[0043] In the above, while the container packaging method according to the present invention has been concretely described based on the embodiment with reference to the figures, the invention is by no means limited to that embodiment but may naturally be added with various changes and modifications as come within the scope of the appended claims.

[0044] For example, in the above described embodiment, the double line seal 5, 6 is formed in addition to the strip seal 3, but omitting the strip seal 3, only the double line seal 5, 6 may be provided. Also in this case, the line seal is not necessarily the double line seal 5, 6 but only the line seal 5 of a single line may be provided.

[0045] Moreover, if not the line seal, only the strip seal may be provided if it has the seal projection that projects toward the outer side edge of the corner of the container edge 1 and has a desired sealing ability.

[0046] Also, in the embodiment as illustrated, the non-sealed portion C is provided between the outer side edge of the corner of the container edge 1 and the projecting end of the seal projection 7 that projects toward the outer side edge of the corner of the container edge 1 so that, when the film begins to be peeled at the corner, the peeling force of the film may surely act concentratedly on the projecting end of the seal projection 7. However, to provide this non-sealed portion C is not essential.

[0047] Furthermore, in the embodiment as illustrated, the present invention is applied to all of the four corners of the container edge 1 but, if the container package is made such that an opening starting place of the container is clearly indicated by an arrow or the like, then the present invention may be applied, for example, only to one corner of the four to which the indication of opening is clearly made. 

What is claimed is:
 1. A container packaging method for packaging a container, having a container edge and being filled with an article, by covering an upper opening face of said container by a film and effecting a seal of an overlapped portion of said container edge and said film, comprising the step of effecting said seal at a corner of said container edge in a shape that said seal has its corner end projected toward an outer side edge of the corner of said container edge.
 2. A container packaging method as claimed in claim 1, further comprising the step of providing a non-sealed portion between a projected end of said seal and the outer side edge of the corner of said container edge.
 3. A container packaging method as claimed in claim 1 or 2, wherein said seal at the corner of said container edge has its inner side edge formed in a cornered shape.
 4. A container packaging method as claimed in claim 3, wherein said seal is formed in a line seal.
 5. A container packaging method as claimed in claim 4, wherein said line seal is formed in a multiple line seal having a plurality of line seals and said plurality of line seals at the corner of said container edge are connected to one another in a substantially diagonal direction of said container.
 6. A container packaging method for packaging a container, having a container edge and being filled with an article, by covering an upper opening face of said container by a film and effecting a seal of an overlapped portion of said container edge and said film, comprising the step of effecting said seal between said container edge and said film, covering the upper opening face of said container, by an overlapped seal of a strip seal and the line seal mentioned in claim 4 or 5, said strip seal having a portion that is sealed partially weakly at an outer side portion of a corner of said container edge. 